The present invention relates to wet shaving systems of the blade type and more particularly to a shaving system having a movable blade positioned within a blade cartridge or the like.
During the shaving process, shavers have long sought a wet shaving system which provides a smooth and comfortable shave without having annoying cuts and abrasions. In order to accomplish this objective, it has been known in the art to utilize multiple blade shaving systems which provide independent movement of the blades relative to the blade cartridge. (See, U.S. Pat. No. 4,168,571).
Typically, such shaving systems include two blades disposed parallel to one another so as to provide first and second cutting edges which successively engage the shaving surface in a predetermined spaced relationship. The use of multiple blades operates to provide a close, more efficient shave. Further, the independent movable blades permit the shaving geometry of each blade to adapt to the various conditions encountered during the shaving process in an effort to reduce nicks and cuts.
The terms utilized to define the various geometric relationships between the blades, the various elements of the blade cartridge and the shaving surface include "shaving plane", "blade exposure" and "shaving angle". The term "shaving plane" means the plane tangent to skin engaging surfaces, for example a guard and a cap, which are disposed on both sides of the blade so as to engage the shaving surface before and after engagement by the blade. The term "blade exposure" means the distance by which the blade edge projects forwardly of the shaving plane. Finally, the term "shaving angle" means the acute angle between the plane tangent to the cutting edge of the blade and the shaving plane.
Various approaches have been used to enable the shaving blade to move relative to the blade cartridge or razor body in response to shaving forces encountered during the shaving process in an effort to present the correct blade exposure and shaving angle.
One approach disclosed in prior art patents illustrates a blade cartridge comprising two blades separated by a spacer with the blades and the spacer attached to a cap to form a unitary assembly. The blade assembly is movable between various blade exposures and shaving angles within various degrees of control and direction in response to forces encountered during shaving. For example, Ciaffone et al., U.S. Pat. No. 4,461,079, discloses a razor cartridge comprising a body portion 10 which includes a guard bar 12 (FIGS. 1-5). The guard bar 12 defines a leading skin-engaging surface fixed to the body portion. A rear beam 17 spans end walls 14 and 16 of the body portion 10 and a medial support member 13 to join the front of the cartridge 12 to the end thereof. A plurality of generally flat coplanar segments 18,19,21,22, each having an opening 23, are hinged to the rear beam 17 by mating webs 24,26,27,28 (col. 2, lines 50-52). Collectively, the segments 18,19,21,22 define a blade seat which is operable to pivot about the beam 17, thereby changing the attitude of blade edge relative to guard bar 12 (col. 2, lines 53-57). A cap 33 is apparently placed above an assembly of two skin-engaging blades 34,36, straddling a spacer 37 (FIG. 3). The two blades and the spacer are secured to one coplanar segment 21 of the blade support or blade seat by a conventional rivet 38 to form a rigid unit. A hinge 27 connects the coplanar segment 21 to the rear-beam 17 (col. 3, lines 1-8). As compared to the position of the blade edges relative to the guard bar at the normal or free position set in accordance with a predetermined blade geometry (FIG. 3), a change in blade geometry occurs during the course of shaving when a shaving force F causes the blade package to rotate or pivot about rear-beam 17 in the direction of arrow R where the blade edges are rendered less "aggressive" (FIG. 4, col. 3, lines 13-23). Upon relaxation of shaving forces, the elastic memory of hinges 24,26,27,28 forces the blade seat, and therefore the blade edges, to return to their normal position (FIG. 3., col. 3, lines 24-26).
In an alternative embodiment, Ciaffone et al. shows the blade seat is hinged to a front beam 175 by webs 240,260,270,280 (FIGS. 6-10, col. 3, lines 46-48). Upon exertion of a shaving force F' (FIG. 9) onto the cap 330, the coplanar segments 180,190,210 and 220, move in the direction of the arrow R (FIG. 9) to provide a more aggressive edge exposure (col. 4, lines 1-9). As in the embodiment of FIGS. 1-5, the elastic memory of the hinges 240,260,270,280 forces the blade edges to return to the free position when shaving forces are released (col. 4, lines 11-13).
Oldroyd et al., U.S. Pat. No. 4,063,354, discloses a shaving unit wherein a blade unit comprises two blades separated by a spacer 5 (FIGS. 13-16). A resiliently flexible metallic or plastic guard 3 is secured to the blade unit by spot welding or other means (col. 3, lines 26-28). The blade unit, which is illustrated in its normal forward position of maximum blade exposure in FIG. 13, can bow rearwardly under pressure applied during shaving to carry the blade unit along a plane to the rear, relative to the platform 1 and cap 4. This reduces blade exposure but increases the shaving angle, as indicated by dotted lines 3' in FIGS. 13 and 15 (col. 3, lines 26-37).
Althauset et al., U.S. Pat. No. 5,074,042, discloses a shaver head comprising two staggered blades 7 embedded in a blade block 6 (FIG. 3). A cover cap portion 9 covers the top side of the blade block 6 (col. 3, lines 12-15). A spring 14 is placed between the blade block 6 and a body 2. The blade block 6, together with the two staggered blades 7, can swivel about an axis A (col. 3, lines 17-43). During shaving, pressure is applied to the razor blade unit, thereby causing the blade block 6 to swivel and alter shaving geometry of the blades (col. 3, lines 46-60).
Jacobson U.S. Pat. Nos. 4,442,598, 4,378,634 and 4,270,268 disclose a razor blade assembly including a body member 2 having blade means 36,36' being independently movable in response to spring finger biasing means 18,18' integral with the body member. In the Jacobson patents, the spring fingers 18,18' move the blade means 36,36' along planes defined by slots 16 in end portions 4,6 of the body member 2.
In all of the aforementioned patents, the blade members either engage movable spring fingers formed integral with the blade cartridge, or are mounted permanently to a platform which is movably connected to the blade cartridge. These methods of providing a movable blade necessitate an elaborate and expensive molding procedure to create a blade cartridge having either integral spring fingers or a movable blade platform. While it has been noted that blades movable relative to the shaving surface during the shaving process are advantageous, it is desirable to eliminate the need for the elaborate molding process required by the movable blade assemblies of the prior art.
Additionally, prior art shaving systems have attempted to reduce the uncomfortableness in shaving caused by the frictional drag of the razor across the skin in conjunction with the force necessary to sever the hair protein structure or whisker. One known method of reducing the frictional drag is shown in U.S. Pat. No. 4,170,821 issued to Booth. As described in Booth, a lubricating agent commonly referred to as a "lube strip" is cemented to the cap portion of the blade cartridge to reduce the frictional forces between the razor and the skin.
However, such systems suffer from various drawbacks. First, a significant portion of the blade cartridge not containing any friction reducing agent remains in contact with the skin. For example, the ends of the blade cartridge extending perpendicular to the cutting edge remain in contact with the skin. As such, the frictional drag encountered during shaving remains significant. Second, the requirement of producing and cementing an additional "lube strip" to the blade cartridge increases manufacturing costs.